/*
 * [New BSD License]
 * Copyright (c) 2011-2012, Brackit Project Team <info@brackit.org>  
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Brackit Project Team nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.brackit.xquery.function.fn;

import org.brackit.xquery.QueryContext;
import org.brackit.xquery.QueryException;
import org.brackit.xquery.atomic.Int32;
import org.brackit.xquery.atomic.IntNumeric;
import org.brackit.xquery.atomic.QNm;
import org.brackit.xquery.function.AbstractFunction;
import org.brackit.xquery.module.StaticContext;
import org.brackit.xquery.sequence.BaseIter;
import org.brackit.xquery.sequence.LazySequence;
import org.brackit.xquery.xdm.Item;
import org.brackit.xquery.xdm.Iter;
import org.brackit.xquery.xdm.Sequence;
import org.brackit.xquery.xdm.Signature;

/**
 * Implementation of predefined function fn:insert-before($arg1, $arg2, $arg3)
 * as per http://www.w3.org/TR/xpath-functions/#func-insert-before
 * 
 * @author Max Bechtold
 * 
 */
public class InsertBefore extends AbstractFunction {

	public InsertBefore(QNm name, Signature signature) {
		super(name, signature, true);
	}

	@Override
	public Sequence execute(StaticContext sctx, QueryContext ctx, Sequence[] args)
			throws QueryException {
		final Sequence s = args[0];
		IntNumeric p = (IntNumeric) args[1];
		final Sequence i = args[2];

		if (p.cmp(Int32.ONE) < 0) {
			p = Int32.ONE;
		}
		final IntNumeric pos = p;

		if (s == null) {
			return i;
		} else if (i == null) {
			return s;
		}

		return new LazySequence() {
			final Sequence seq = s;
			final Sequence ins = i;
			final IntNumeric p = pos;

			@Override
			public Iter iterate() {
				return new BaseIter() {
					private IntNumeric next = Int32.ONE;
					private Iter itSeq;
					private Iter itIns;

					@Override
					public Item next() throws QueryException {
						if (itSeq == null) {
							itSeq = seq.iterate();
							itIns = ins.iterate();
						}

						Item nextSeq = null;
						Item nextIns = null;

						if (next.cmp(p) < 0) {
							if ((nextSeq = itSeq.next()) != null) {
								next = next.inc();
								return nextSeq;
							} else {
								next = p;
							}
						}

						if (next.cmp(p) == 0) {
							if ((nextIns = itIns.next()) != null) {
								return nextIns;
							} else {
								next = next.inc().inc();
							}
						}

						return itSeq.next();
					}

					@Override
					public void close() {
						itSeq.close();
						itIns.close();
					}
				};
			};
		};
	}

}
